1. Technical Field
The present invention relates in general to computer hardware systems, and in particular to such computers utilized in industrial applications. Still more particularly, the present invention relates to the modular construction of such computers, wherein the computer system is more easily serviced and/or upgraded.
2. Description of the Related Art
Typical computer systems comprise a housing or enclosure that contains the individual components of the computer system, which may include a motherboard or planar circuit board that includes the central processing unit (CPU), I/0 circuit boards, DASD, power supply, disk drives, and cables interconnecting these components. Generally, each of these components is individually removable from within the housing for repair or replacement.
One or more accessory circuit boards or cards are provided within the housing to expand or modify the input and output (I/O) capabilities of the computer system. Because it is expected that these accessory cards will be removed for repair or replacement rather frequently, the accessory cards are grouped in a subenclosure within the housing commonly known as a "card cage." The card cage generally is designed to group the accessory cards together for easy access and to provide mechanical and electrical connections to facilitate the installation and removal of the accessory cards.
U.S. Pat. No. 4,964,017, Oct. 16, 1990 to Jindrick et al. discloses a housing for a computer system that includes a card cage as described above. In one embodiment, the card cage, and accessory cards therein, are electrically connected to a motherboard or planar circuit board mounted on the floor of the main housing or enclosure or the computer system. Alternatively, the card cage and accessory cards therein, may be electrically connected to a passive backplane circuit board, which contains no active electrical components. The passive backplane circuit board is, in turn, electrically connected to one or more circuit boards, which include at least the CPU circuit board, the memory circuit board, and I/O circuit boards. It appears that the card cage disclosed by Jindrick may be removable from the remainder of the computer housing to facilitate access to the card cage and the various accessory cards contained therein.
The computer system disclosed by Jindrick is typical of industrial computer systems, which achieve flexibility in configuration and ease of repair by employing the passive backplane circuit board as a central connection member to which other components making up the computer are connected. However, the bulk of development in computer technology is occurring in the more commercial personal computer (PC) arena, in which the motherboard or planar circuit board, which contains all of the basic elements of the computer system (e. g. CPU, memory, and I/O controller), is the central "building block" of the computer system. Thus, advances in technology generally are first made available on a commercial basis in the form of motherboards or planar circuit boards incorporating these advances. Prior-art computer systems, like that disclosed by Jindrick, are not configured to take advantage of commercially available technological advances embodied in motherboards or planar circuit boards.
As advances are made in CPU and support technologies, it becomes advantageous to upgrade existing computer systems to take advantage of the processing power provided by these advances. Changes in CPU and support technologies often necessitate replacement of the mother board or planar circuit board along with the CPU. Additionally, differences in the architecture of the CPU and its associated planar circuit board may require changes in the I/O capabilities of the computer system, necessitating replacement of the previously mentioned accessory cards.
Because the planar circuit board and accessory circuit boards or cards are among the components most likely to require replacement or repair, a need exists for an improved computer system and card cage containing both the planar circuit board that includes a CPU, and at least one accessory circuit board, wherein the card cage, planar circuit board, and accessory circuit boards can be removed together as a unit from the housing of the computer system for replacement or repair.